多点变加载路径下实现大型曲面近净成形的原理与方法

As more and more three-dimensional surfaces are applied in engineering, there are more and more demands for irregular surface parts with large curvature; however, traditional stretching technique couldn't be widely used to form such kind surface parts because of high production cost and forming defects. The near net forming for surface part based on controllable loading path at multi-point is a new sheet metal forming method which is created to solve the problem in manufacturing curved sheet metal surface parts with lower-cost and high quality. The basic idea of the process is to replace the loading setup in traditional stretching by loading unit array and the controllable stretching loads are applied at discrete points on the both ends of sheet metal. By controlling the loading path reasonably, the transition zone of the sheet metal in stretch-forming process can be reduced, the material utilization can be improved and the near net forming for surface parts can then be realized, in addition, the forming process is optimized, the uniformity of the deformation distribution of the material will be improved, and consequently the forming defects are avoided. This project will expound the new principle of the stretch-forming for surface parts based on discretely controllable loading, set up near net stretch-forming process for three-dimensional surfaces, and set up the design method for controlling the loading trajectories in the stretch-forming process of curved surface oriented to uniform deformation and forming defects controlling, establish the basic theory on the near net forming of three-dimensional surfaces. The project will solve the key technological problems on the loading control, and then develop an experimental device. A series of forming tests will be carried out to demonstrate the validity and feasibility of the near net forming process. The method presented in this project is of originality, it can satisfy the urgent requirement for irregular surface parts with large curvature in the fields such as high speed train manufacturing and modern architecture fabrication, the method has a very wide application prospect.

随着空间曲面的工程应用越来越多，大曲率复杂曲面零件的需求量越来越大。但传统的拉形技术成本高、易出现成形缺陷，难以广泛应用。多点变加载路径曲面近净成形是为解决曲面零件的低成本、高质量加工问题而创建的板料成形新方法。其基本思路是将加载机构离散成加载单元阵列，在板料两端的系列离散点上施加可控的拉形载荷，通过对加载路径的合理控制，减小拉形工艺过渡区，提高材料利用率，实现曲面的近净成形，并优化成形过程，改善变形均匀性，从而避免成形缺陷。本项目将阐明基于离散可控加载路径的曲面拉伸成形原理，建立三维曲面的近净成形方法，建立面向变形均匀性与缺陷控制的曲面拉伸成形加载路径设计方法，形成变加载路径曲面成形的基本理论。研制出实验装置，通过系统的成形实验证明变加载路径曲面成形的有效性与可行性。本项目提出的方法具有原创性，可满足高速列车制造及现代建筑等领域对大型曲面零件成形技术的迫切需求，具有广阔的应用前景。

多点变加载路径曲面近净成形是为解决曲面零件的低成本、高质量加工问题而创建的板料成形新方法，其基本思路是将加载机构离散成加载单元阵列，在板料两端的系列离散点上施加可控的拉形载荷，基于对加载路径的合理控制，一方面，优化曲面成形过程，控制变形分布，按接近均匀变形或最小变形的加载路径成形曲面零件，从而避免成形缺陷，获得最佳成形效果；另一方面，有效地减小板料的拉形工艺过渡区，从而节省材料，实现曲面的近净成形。. 本项目通过系统的理论分析、数值模拟与成形实验，对多点变加载路径曲面成形的原理与工艺进行了研究。建立了多点变加载路径的三维曲面拉伸近净成形方法，取得了变形规律、成形缺陷控制、成形过程设计方法、离散加载模式控制与优化等基础研究成果；建立了大变形量、大曲率以及大型曲面的多点变路径对压成形与控制方法，实现了夹芯复合板三维曲面的多点塑性成形，取得了复合板曲面塑性成形规律、可成形性、成形缺陷分析等方面的研究成果；建立了多点变加载路径下的曲面连续成形方法，取得了侧弯形三维曲面零件连续辊压成形以及复合板曲面辊弯成形方面的研究成果；研制了用于多点变加载路径三维曲面成形的实验装置，通过变加载路径曲面拉伸成形及复合板三维曲面多点成形的实验研究，获得了多种形状的曲面零件，证明曲面成形方法的有效性与可行性。. 本项目在多点变加载路径曲面拉伸成形、对压成形以及连续成形方面的研究成果，为工程中大型曲面的加工提供了经济、实用的新技术，可满足许多行业对不同形状曲面零件成形技术的需求。随着空间曲面的工程应用越来越多，大曲率复杂曲面零件的需求量越来越大。在飞机、航天器、汽车、高速列车、轮船、舰艇等交通与运载工具制造业以及现代建筑业都涉及大量的大型三维曲面，本项目的研究成果具有广阔的应用前景。